So-called rimless eyeglasses, also known as pierced lens eyeglasses because of the holes formed through the thickness of the lenses in order to fasten the frames thereto, are becoming more and more widespread.
Reference can be made to the following documents: WO—2004/003632 A, EP—1 107 042 A, WO—96/05535 A, U.S. Pat. No. 6,447,117 A, WO—00/26716 A, EP—1 382 988 A, WO—03/014804 A, WO—02/095482 A, and WO—02/095481 A.
In most of the above-mentioned arrangements, in order to fasten each component element of the frame, i.e. the bridge and the two side branches, there is provided a through hole in the corresponding lens, together with an open side notch, or else two through holes are provided.
Document U.S. Pat. No. 5,835,183 A provides for hinge elements that are fastened to the side portions of the lenses via respective S-shaped parts, each having a free end passing through a through hole, with the central portion passing through an open side notch. The end portion, thus forming a loop, is designed to clamp resiliently onto the intermediate portion of the lens, where the clamping is further reinforced by elements seeking to increase friction resistance, in particular by means of teeth that bite into the surface of the corresponding lens from within the through hole and within the open side notch. Nevertheless, that presents the drawback of spoiling the surface of the lens, which surface is thus planed by the teeth, thereby weakening the zone of the lens that is clamped between the two portions of the clamp-forming branch, which zone is sometimes narrow.
Document JP—2002/318 372 A and EP—0 814 359 illustrate wire frames in which the branches, either including hinges or without hinges but suitable for deforming in bending, present hooked-shaped distal ends, with a terminal portion of each branch passing into an open side notch of the lens and with a short clamping portion passing into a hole in the lens, these two portions forming a clamp that presses against the portion of the lens that lies between the hole and the open side notch in order to ensure that the branch is held in place. Clamping of the lens is further reinforced in the arrangement of document JP—2002/318 372 A by the way the short portion is inclined towards the terminal portion of the branch, and by the corresponding inclination of the axis of the hole through the lens, possibly together with a bushing interposed in the notch so that its flange forms a spacer that prevents clamping being released.
Document WO—02/21193 A shows a variant of the above frames in which the side branches with hook-shaped distal ends are curved behind the lenses after they have been threaded through, and they are then held in place by respective folds adjacent to the rear faces of the lenses. Such a process is time-consuming and requires numerous operations that can only be performed manually.
Furthermore, proposals have been made to provide eyeglasses of the rimless type in which the side branches are deformable in bending without any hinge. For that purpose a forming technique is used that takes advantage of the shape memory capacities of certain metal alloys. In order to fasten hingeless and bendably-deformable branches of those types, it is general practice to engage pegs that pass through holes, as described for example in document WO—03/083553 A and U.S. Pat. No. 5,367,344 A.
In most circumstances, the fastener ends of the side branches present complex configurations with multiple bends, thereby implying a fabrication cost that is high. In addition, it is sometimes necessary to perform such bending in situ, after threading an end of the branch that is rectilinear and not yet bent through a hole in the lens, and that is particularly inconvenient for the operator.
More recently, eyeglasses of the rimless type have been proposed that have branches of hingeless and bendably-deformable wire structure, each side branch comprising a main portion and a distal end extending said main portion and arranged to fasten to the side zone of the lens, said distal end being generally J-shaped and including a holder portion passing through a through hole in the lens with a flexible clamping bushing being interposed there between that suffices on its own to hold the distal end in place, and an antirotation portion passing into an open side notch or into another through hole in the lens, without clamping the lens between said holder portion and said antirotation portion, the central portion that interconnects the holder portion and the antirotation portion extending in the vicinity of the front face of the lens, as taught in document U.S. Pat. No. 7,264,348 B2 of the Applicant.
The teaching of that document is to use side branches of hingeless and bendably-deformable wire structure so as to have a unitary wire component that can be put into place merely by being threaded through the lens from its front face, passing through the through hole, with the lack of any extra thickness making threading easy, in particular while passing through the flexible clamping bushing that is already put into place in the associated through hole.